Android中使用HttpURLConnection实现GET POST JSON数据与下载图片

Android6.0中把Apache HTTP Client所有的包与类都标记为deprecated不再建议使用

所有跟HTTP相关的数据请求与提交操作都通过HttpURLConnection类实现，现实是

很多Android开发者一直都Apache HTTP Client来做andoird客户端与后台HTTP接口数

据交互，本人刚刚用HttpURLConnection做了一个android的APP，不小心踩到了几个

坑，总结下最常用的就通过HttpURLConnection来POST提交JSON数据与GET请求

JSON数据。此外就是下载图片，下载图片分为显示进度与不显示进度两种。其中提交

数据的时候涉及中文一定要先把中文转码成utf-8之后在POST提交，否则就会一直遇到

HTTP 400的错误。

一：GET请求JSON数据的例子

public UserDto execute(String... params) {InputStream inputStream = null;HttpURLConnection urlConnection = null;try {// read responseURLEncoder.encode(para, "GBK");String urlWithParams = DOMAIN_ADDRESS + MEMBER_REQUEST_TOKEN_URL + "?userName=" + java.net.URLEncoder.encode(params[0],"utf-8") + "&password=" + params[1];URL url = new URL(urlWithParams);urlConnection = (HttpURLConnection) url.openConnection();/* optional request header */urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8");/* optional request header */urlConnection.setRequestProperty("Accept", "application/json");/* for Get request */urlConnection.setRequestMethod("GET");int statusCode = urlConnection.getResponseCode();/* 200 represents HTTP OK */if (statusCode == 200) {inputStream = new BufferedInputStream(urlConnection.getInputStream());String response = HttpUtil.convertInputStreamToString(inputStream);Gson gson = new Gson();UserDto dto = gson.fromJson(response, UserDto.class);if (dto != null && dto.getToken() != null) {Log.i("token", "find the token = " + dto.getToken());}return dto;}} catch (Exception e) {e.printStackTrace();} finally {if (inputStream != null) {try {inputStream.close();} catch (IOException e) {e.printStackTrace();}}if (urlConnection != null) {urlConnection.disconnect();}}return null;
}

二：POST提交JSON数据

public Map<String, String> execute(NotificationDto dto) {InputStream inputStream = null;HttpURLConnection urlConnection = null;try {URL url = new URL(getUrl);urlConnection = (HttpURLConnection) url.openConnection();/* optional request header */urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8");/* optional request header */urlConnection.setRequestProperty("Accept", "application/json");dto.setCreator(java.net.URLEncoder.encode(dto.getCreator(), "utf-8"));// read response/* for Get request */urlConnection.setRequestMethod("POST");urlConnection.setDoOutput(true);DataOutputStream wr = new DataOutputStream(urlConnection.getOutputStream());Gson gson = new Gson();String jsonString = gson.toJson(dto);wr.writeBytes(jsonString);wr.flush();wr.close();// try to get responseint statusCode = urlConnection.getResponseCode();if (statusCode == 200) {inputStream = new BufferedInputStream(urlConnection.getInputStream());String response = HttpUtil.convertInputStreamToString(inputStream);Map<String, String> resultMap = gson.fromJson(response, Map.class);if (resultMap != null && resultMap.size() > 0) {Log.i("applyDesigner", "please check the map with key");}return resultMap;}}catch(Exception e){e.printStackTrace();}finally{if (inputStream != null) {try {inputStream.close();} catch (IOException e) {e.printStackTrace();}}if (urlConnection != null) {urlConnection.disconnect();}}return null;
}

三：下载图片显示下载进度

package com.example.demo;import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;
import android.util.Log;public class ImageLoadTask extends AsyncTask<String, Void, Bitmap> {private Handler handler;public ImageLoadTask(Handler handler) {this.handler = handler;}protected void onPostExecute(Bitmap result) {Message msg = new Message();msg.obj = result;handler.sendMessage(msg);}protected Bitmap doInBackground(String... getUrls) {InputStream inputStream = null;HttpURLConnection urlConnection = null;try {// open connectionURL url = new URL(getUrls[0]);urlConnection = (HttpURLConnection) url.openConnection();/* for Get request */urlConnection.setRequestMethod("GET");int fileLength = urlConnection.getContentLength();int statusCode = urlConnection.getResponseCode();if (statusCode == 200) {inputStream = urlConnection.getInputStream();byte data[] = new byte[4096];long total = 0;int count;ByteArrayOutputStream output = new ByteArrayOutputStream();while ((count = inputStream.read(data)) != -1) {total += count;// publishing the progress....if (fileLength > 0 && handler != null) {handler.sendEmptyMessage(((int) (total * 100 / fileLength)) - 1);}output.write(data, 0, count);}ByteArrayInputStream bufferInput = new ByteArrayInputStream(output.toByteArray());Bitmap bitmap = BitmapFactory.decodeStream(bufferInput);inputStream.close();bufferInput.close();output.close();Log.i("image", "already get the image by uuid : " + getUrls[0]);handler.sendEmptyMessage(100);return bitmap;}} catch (Exception e) {e.printStackTrace();} finally {if (inputStream != null) {try {inputStream.close();} catch (IOException e) {e.printStackTrace();}}if (urlConnection != null) {urlConnection.disconnect();}}return null;}}

总结：使用HttpURLConnection提交JSON数据的时候编码方式为UTF-8

所有中文字符请一定要预先转码为UTF-8，然后在后台服务器对应的API

中解码为UTF-8，不然就会报错HTTP 400。